Sc-substituted La0.6Sr0.4FeO3−δ mixed conducting oxides as promising electrodes for symmetrical solid oxide fuel cells

Abstract

The main barrier to symmetrical solid oxide fuel cells (SOFCs), where the same catalytic materials are used simultaneously as the anodes and the cathodes, is to identify a redox-stable catalyst that exhibits superior catalytic activities for both fuel oxidation and oxygen reduction reactions. Here we report a Sc-substituted La0.6Sr0.4FeO3−δ oxide, La0.6Sr0.4Fe0.9Sc0.1O3−δ, that shows great promise as a new symmetrical electrode material with good structural stability and reasonable conductivities in air and hydrogen. We further demonstrate that nano-scale La0.6Sr0.4Fe0.9Sc0.1O3−δ catalysts impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3−δ backbones exhibit good catalytic activities for oxygen reduction and hydrogen oxidation reactions and thereby yield low polarization resistances, e.g., 0.015 Ω cm2 in air and 0.29 Ω cm2 in hydrogen with appropriate current collection at 800 °C. Thin La0.9Sr0.1Ga0.8Mg0.2O3−δ electrolyte fuel cells with such symmetrical La0.6Sr0.4Fe0.9Sc0.1O3−δ catalysts showed maximum power densities of 0.56 and 0.32 W cm−2 when operating on 97% H2–3% H2O at 800 and 700 °C, respectively.